1. Field of the Invention
The present invention relates to semiconductor packages, and more particularly, to a package having a light-emitting element and a fabrication method thereof.
2. Description of Related Art
Along with the development of semiconductor technologies, various semiconductor packages have appeared. Fabrication of a light-emitting diode (LED) package involves frame design (including light extraction and heat dissipation), chip selection and arrangement, chip bonding, gold wire formation, phosphor coating, silicone lens disposing and so on. These fabrication processes greatly affect the characteristics of the LED package such as thermal performance (thermal resistance), luminous flux, light-emitting efficiency, correlated color temperature (CCT), color rendering index (CRI), light color uniformity, lifetime and so on.
Generally, the phosphor coating process plays a key role in achieving high light color uniformity and high luminous flux. Referring to FIG. 1A, a fluorescent layer 14 is conventionally formed by uniformly distributing a phosphor powder in an encapsulant through dispensing. However, under long-term use, particles 140 of the fluorescent layer 14 can be non-uniformly distributed due to deposition. As such, light from the LED chip 11 takes different paths and portions of the fluorescent powder distant from the LED chip 11 reflect light, thus resulting in non-uniform light color distribution and making it difficult to meet user demands.
Accordingly, other coating techniques are developed, such as a conformal coating method of FIG. 1B, a thin film attaching method of FIG. 1C or a spray coating method of FIG. 1D.
However, in FIG. 1B, an electrophoresis process needs to be performed for coating the fluorescent layer 14 on the LED chip 11. Such an electrophoresis process requires specific devices, thus resulting in a high fabrication cost.
Further, in FIG. 1C, a thin film 14′ of phosphor powder is attached to a transparent material 15 around the LED chip 11 so as to be positioned distant from the LED chip 11 that dissipates a large amount of heat. However, as the transparent material 15 has a low refractive index (a resin material has a refractive index of 1.54 and the phosphor powder has a refractive index of 1.8), it results in a low light-emitting efficiency of the LED chip 11.
Furthermore, the spray-coating method of FIG. 1D can only be applicable to a COB (chip on board) type LED package instead of an LED package with the substrate thereof having a recess. If a spray coating process is performed to a substrate 10 having a recess 100, particles 140 (phosphor powder) of the fluorescent layer 14 can be sprayed onto a reflective layer 16 on inclined surfaces of the recess 100, thus reducing the reflective area of the reflective layer 16 and accordingly decreasing the light-emitting efficiency of the LED chip 11.
Therefore, there is a need to provide a fabrication method of a package having a light-emitting element so as to overcome the above-described drawbacks.